Running out at 1/4 tank sounds like someone swapped the supply and return lines. How much does it take when you fill it up?
I'd start by replacing the inline fuel filter (the one with the 90 degree bend, looks like it belongs on a lawn mower), and the canister fuel filter.

If your filters are clogging up, especially if someone swapped the fuel lines, it sounds like you have sludge or something in your tank. Hopefully you have a clear inline filter, if it's full of black goo your tank has sludge in it.

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1984 300TD -- summer daily driver
Many others that aren't Mercedes...